Building of a visibility area by a matrix of heights as the raster image |
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The visibility zone is a raster image within one or several sectors of the review, in places of crossing of which parameter of construction operates the Visibility of zones of crossing (from all points or at least from one). Color of a pixel of the raster image within review sector is defined by position of sector top on a surface of relief, and also by values of parameters the Observation height and the Increment of an observed point. For determining a visibility of a point (pixel) the beam is constructed from the sector top to the given point with the account of parameters the Observation height and the Increment of an observed point. Further it is defined - whether this beam is not interrupted by a surface on the way to a determined point. If the surface closes a defined point from the observation point, then the defined point is painted by the color of "invisibility" specified in parameter Color of non visible area. The step of calculations at visibility area construction is equal to the size of an element (discrete) of an initial matrix of heights of a relief. The size of an element of a resulting raster is equal to the element size of a matrix of heights. For determining the visibility areas it is necessary to construct one or several sectors of the review on a map, having denoted the observation point and border of sector by pressing the left mouse button. In the dialogue window of Building a visibility area it is offered to choose a file name (a raster format) in which the results of construction, a filling color of invisible areas in review sector, observation height in meters, degree of a transparency and a mode of construction of crossed sectors will be written down. For areas of sectors intersection there are modes: - visibility from all view points; - visibility, at least, from one point.
In the mode Visibility from all points those areas are considered visible (transparent) in a zone of sectors intersection that are visible from all points of observation. In the mode of Visibility at least from one point those areas are considered visible (transparent) in a zone of sectors intersection that are visible, at least, from one point of observation. All session parameters (file name, color, degree of raster's visibility, etc.) are saved in the file PANORAMA.INI and are restored at the subsequent loading. |
This mode allows to define visibility areas on a map, using the information from a matrix of heights.